This invention relates to a pickup device for an optical disc and an objective lens protective member used therefor.
A pickup device for an optical disc replay device in which an optical disc such as a CD (compact disc) or DVD (digital versatile disc) is inserted in an exposed state has an objective lens for focusing a laser beam on the information recording surface of the optical disc, with the objective lens arranged at a small distance of about 2 mm from the optical disc. The distance between the optical disc and the objective lens is expected to further decrease as the information recording density of optical discs increases. The objective lens is adapted to be moved in a direction normal to the optical disc surface and in a radial direction of the optical disc together with its retaining portion for focus adjustment of the laser beam and tracking adjustment.
Thus, in such a pickup device, the objective lens and the optical disc, which are arranged close to each other, may contact each other by vibration or shock, thus damaging the information recording surface of the optical disc or the objective lens. In order to prevent them from contacting each other, a soft objective lens protective member is provided so as to protrude from the objective lens toward the optical disc.
As such an objective lens protective member, there are known one in which a shock-absorbing material such as wool felt is fitted (JP patent publication 2593998), one in which a protrusion is provided which is formed of a plastic softer than the optical disc (JP patent publication 2-54433), one in which a protector made of silicon rubber is fitted (JP patent publication 11-312322), and one in which a protective lubricating layer is formed on the surface of a resilient metallic plate having a convex surface (JP patent publication 2001-297478).
Such an objective lens protective member has to be not only softer than the material of the optical disc so that it will not damage the information recording surface of the optical disc, but also it has to be elastic to lessen impact of contact with the optical disc, and has to be superior in lubricity so that the friction with the optical disc, which is rotating at a high speed, is low. Further, it is preferably easily mountable on the objective lens retaining portion of a compact pickup device.
Of these four conventional protective members, the first three are relatively easily mountable. But none of them has both resilience and lubricity. On the other hand, the fourth protective member has both resilience and lubricity. But since a resilient metallic plate is formed by insert molding so as to protrude from the objective lens retaining portion and a protective lubricative layer of amorphous carbon film is formed by e.g. ion plating, it is extremely troublesome to manufacture it.
An object of this invention is to make it possible to easily provide an objective lens protective member which can reliably prevent damage to the optical disc on the objective lens retaining portion.